The present invention relates to a pyrogenically produced aluminum oxide, a method for its production and its use.
The paper industry requires readily dispersible fillers which absorb ink rapidly when used in inkjet paper or inkjet films and which help to give colors a high brilliance. The present invention concerns a specially produced aluminum oxide which, by virtue of its properties in corresponding coating slip formulations, is capable of reproducing inks applied by an inkjet printer onto these media containing this special aluminum oxide with very high brilliance and color fidelity.
It also concerns the utilization of this aluminum oxide in the manufacture of ink-receiving layers such as are conventional in inkjet media (e.g. paper, films, fabric, etc.).
The present invention provides a high surface area, pyrogenically produced aluminum oxide, characterised in that the BET specific surface area is greater than 115 m2/g, and the Sears index is over 8 ml/2 g.
In an embodiment of the invention, the aluminum oxide is characterised in that the dibutyl phthalate absorption by the powder measured with a 16 g weighed portion is not measurable (no end-point detection).
The pyrogenically produced aluminum oxide according to the invention can be produced by means of flame oxidation or preferably flame hydrolysis, whereby a vaporizable aluminum compound, preferably chloride, is used as starting material. Such methods are known in the art.
The invention also provides for the use of the herein described aluminum oxide as an ink-absorbing substance in inkjet media.
The invention also provides for the use of the high surface area aluminum oxide herein described as a filler, as a substrate, as a catalytically active substance, as a starting material for the production of dispersions, as a polishing material (CMP applications), as a ceramic raw material, in the electronics industry, in the cosmetics industry, as an additive in the silicone and rubber industry, to adjust the rheology of liquid systems, as a heat stabilizer, in the paint industry.
The pyrogenically produced aluminum oxide according to the invention as an ink-absorbing substance displays the following properties:
Good optical density and dot resolution, high ink absorption, rapid ink drying time, no bleeding (running together of inks), good water resistance after drying, no color shifts, no breakdown of inks after extended periods.
In comparison to known commercially available products (Aluminumoxid C and Aerosil MOX 170, both from Degussa-Hxc3xcls AG), the aluminum oxide according to the present invention exhibits very good properties for the manufacture of inkjet receiving layers, both alone and in combination with other fillers. It is characterised by enhanced brilliance and depth of color. These properties are of particular benefit in ink-receiving layers that are used for photographic quality reproduction. Weather resistance to water and light is also improved, which is advantageous for outdoor applications.